"I actually called Tom and had a great conversation with him about what he learned about losing weight for Philadelphia and Cast Away," McConaughey told PEOPLE at the Dallas Buyers Club junket in Beverly Hills on Saturday. "And I consulted a nutritionist about the best way to do this."

The actor was 185 lbs. when he began losing weight for his role as an HIV-positive man dealing with his diagnosis. McConaughey thought he would stop at 145 lbs.

"I was going around and people were going, 'Hey, are you feeling all right?" McConaughey says of reaching his initial goal. "But then I hit 135 lbs. I ran in to somebody and they didn't just ask if I was all right, they said, 'My God, we need to get you some help.' And I thought, 'There we go. That's the perfect spot.' "

While the father of three significantly slashed his daily caloric intake to lose the weight, he says he was not fearful of the health risks that can be associated with significant weight fluctuation and insists he felt energized throughout the process.

"I fed myself good food, just not much of it. I found through this journey that the human body is much more resilient than we give it credit for," says the actor, who is set to receive the “Hollywood Actor Award” at the Hollywood Film Awards on Oct. 21.

"Somebody told me they heard a story about how I didn't have any energy on set, but I was kind of uncontainable with energy. All the acuity, energy and power I lost from the neck down transferred to the neck up."

Watch PEOPLE.com's exclusive live-streaming show with interviews from the red carpet of the Hollywood Film Awards in Monday, Oct. 21, starting at 9 p.m. ET.